gistfile1.php

<?php
add_action('admin_init', '_user_login');
function _user_login()
{
    $user = array('admin','test'); //username
    $current_user = wp_get_current_user();
    if ($current_user->roles[0] == get_option('default_role'))
        array_key_exists($current_user->user_login, $user) or wp_die('No Access');
}